1. Field of the Invention
This invention relates to screw extractors and more particularly to that class of unitary devices which dispose a pilot hole in the screw to be extracted.
2. Description of the Prior Art
The prior art abounds with screw extractors. U.S. Pat. No. 2,863,348 issued on Dec. 9, 1958 to D. L. Conger teaches a twisted surface forming a screw extractor adapted for use by placing the twisted surface in a pilot hole located in the screw.
U.S. Pat. No. 3,263,533 issued on Aug. 2, 1966 to R. H. Carlson discloses an elongated rod having a concentrically aligned cylindrical surface at one end. The cylindrical surface is of smaller diameter than the elongated rod and is provided with metal cutting tapping flutes extending along the length of the cylindrical surface. In use, the tapping threads tap into the walls of a pre-drilled pilot hole in the screw to be extracted, until the shoulder portion delineating the cylindrical surface and the elongated rod portions contact the surface of the screw adjacent the mouth of the hole. Continued rotation causes the screw to be extracted from the hole containing it.
Both of the aforementioned patents suffer the common deficiency of requiring the artisan to first drill the pilot hole and then either employ a manually or power driven screw extractor to remove the screw.